Radio receiver



Aug. 16, 1938. E. F. ANDREWS RADIO RECEIVER Original Filed' Oct. 27, 1932 4 Sheets-Sheet 1 EN R .EW mw Rm %N Q NR QR E. F. ANDREWS RADIO RECEIVER Aug. 16, 1938.

Original Filed Oct. 2'7, 1932 4 Sheets-Sheet 2 Aug. 16, 1938. EWS 2,127,488

RADIO RECEIVER Original Filed Oct. 27, 1932 4 Sheets-Sheet 5 f, 114. 113 1.9 .2 7 fly f 201/ ell/Z01. fidg rd 171096105 1938. E. F. ANDREWS 2,127,488

RADIO RECEIVER Origifial Filed Oct. 2'7, 1932 4 Sheets-Sheet 4 UNITED STATES PATENT orrice 639,821. Patent No, 2, 21, 1937. 22, 1937,

Divided and Serial No. 138,333

103,135, dated this application April 22 Claim!- (Cl. 250-27) "This application is a divisional from my copending application Serial No. 639,821, flied October 27, 1932.

This invention relates to radio receivers and has for-one of its objects the provision of an improved radio receiver adapted for operation on either alternating current or direct current.

A further object of the invention is to provide a radio receiver, suitable for operation with alter- 10 nating current or low voltage direct current, having a simple switching means for turning either supply off or on. One specific object of the invention is to provide an alternating current radio receiver which 15 may be converted to a low voltage direct current receiver by the addition of a cable equipped with an interrupter.

A further object of my invention is to provide a radio receiver which can be operated either 2 in the home from alternating current or in an automobile from the automobile battery.

A further object of my invention is to provide a radio receiver, operable on either alternating current or low voltage direct current, all the 25 component parts of which are in use in either case.

A further object of my invention is to provide a radio set primarily intended for home use on alternating current which will be cheap and elli- 30 cient and which can be adapted to operate from a source of relatively low voltage direct current with a minimum of additional apparatus and cost.

Other objects, advantages. and capabilities of the invention will appear from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, .ln which:

Figure l is a diagram of a radio receiver em- 40 bodying my invention;

Fig. 2 is a diagram of the alternating current cable and switch plug for the-receiver;

Fig. 3 is a diagram of the direct current cable and switch plug for this receiver;

Fig. 4 is a diagram showing the energy part of a modified receiver;

Fig. 5 is a diagram of a direct current cable and switch plug used in the embodiment of the invention illustrated in Fig. 4;

Fig. 6 is a sectional view through the receiver;

Fig. 'l is a plan view thereof with the cover' removed;

Fig. 8 is an elevational view of the receiver, the casing being shown in section;

I pp y Fig. 9 is a diagram showing the energy supply part of a further modified receiver;

Fig. 10 is a diagram of a direct current cable and switch plug used in the embodiment of the invention illustrated in Fig. 9, and

Fig. 11 is a diagram of an alternating current cable and switch plug for this receiver.

Referring to the drawings. the reference numeral l0 designates the antenna while the tubes of the set are designated ii, l2, l3 and I l. The speaker cone is designated and the field coil and the voice coilby the reference numerals l6 and 11, respectively. It will readily be understood from the following description that many novel and valuable features of this invention may be utilized in sets having different circuits and that it is not intended to limit the invention to a set of the wiring system shown. The particular set herein selected for the purpose of illustrating the invention is a simple four tube superheterodyne, the tube 1 I being the first detector and oscillator, tube 12 the intermediate frequency amplifier, tube 13 the second detector, and tube 14 the audio frequency power amplifying tube.

The transformer 18 and rectifying tube It are provided for supplying plate current of appropriate voltage for the operation of the set. The plate of the rectifier I9 is connected to winding 20 of transformer l8. This transformer com prises two other windings 21 and 22.

A group 31, Fig. 1, of contacts 23, 24, 33, 3|, 34, 28 and 36 is mounted on the receiver and is adapted to cooperate with either of the switch plugs 42 and 65 hereinafter described. One end of winding 22 of transformer contact 23. The other end of winding 22 is connected to a magnetically operated interrupter 11 and to contact 29 of a double pole double throw switch 26. Interrupter 11 comprises a magnet, excited by a coil 19, and contacts 80, one of which is stationary and the other carried by a vibrating armature. The connection from winding 22 to the interrupter 11 is completed through coil 19 and contacts 80 to pole of switch 26. Condenser 82 is connected across coil 19 and contacts 80 to prevent arcing at the contacts and to minimize interference resulting from the operation of the interrupter. This interference is further reduced by means of a metallic casing 13 completely shielding the interrupter and connected to the chassis of the set. This casing is preferably lined with sound insulating material. A relatively high resistance 8| may be inserted across the points 80 to reduce the voltage built up across the points.

18 is connected to One end of winding 2| oi transformer |8 connects to contact 24. The other end of winding 2| is connected to a second pole 32 of the double pole double throw switch 28. Contact 33 of the switch is connected to contact 38 and contact 35 is connected to contact 3| and one end 0! winding 28 of the transformer.

The other end of winding 28 connects to plate 46 of a rectifier tube I8. Contact 34 connects to one end of the speaker field coil l6 through a radio frequency choke coil 54. The other end oi field coil |6 connects to the common ground of the chassis. Contact 36 also connects to the chassis. One end of the filaments of tubes |2, l3 and I4 and rectifier tube I8 is grounded to the chassis. The other ends of the filaments are connected together and to pole 25.0f switch 28 by means of conductor 86.

For operation of the set on alternatingcurrent a cable 38, Fig. 2, is provided. This cable consists. of two conductors 48 and 4| connected at one end to the prongs of a plug 38 adapted to plug into a conventional outlet box. The other end of cable 38 carries a switch plug 42 having a plurality of contacts, designated 41, 48, 48, 58, 5|, 52 and 63, corresponding to the contacts 24, 38, 3|, 34, 28, 23 and 36 of group 31 and adapted to be engaged with them respectively when the switch plug 42 is applied to said group. Conductors 48 and 4| are connected to contacts 41 and 48, respectively, of switch plug 42. Contacts 48 and 58 are connected together by a conductor 43 while contacts 52 and 58 are connected together by conductor 44. Contact 5| is left open.

With switch plug 42 engaged with the contacts of group 31 and switch 26 thrown with its poles in the up position, as viewed in Fig. 1, the set is connected for alternating current operation. Winding 2| acts as the primary and connects to the prongs oi plug 38 through switch pole 32, switch contact 33, contacts 24 and 38 of group 31, contacts 41 and 48 of switch plug 42 and conductors 48 and 4| in cable 38.

Winding 22 supplies current to the filaments of tubes 2, I3 and I4 and rectifier tube l8, one end of the filaments being connected by means of conductor 86, switch pole 25, and switch contact 28 to one end of winding 22. The other ends of the filaments are grounded to the chassis and the other end of the winding 22 is likewise grounded to the chassis through contact 23, contact 52, conductor 44, contact 53 and contact 36.

In this condition of switching, the winding 28 of transformer |8 acts as the secondary. One end of winding 28 connects to contact 3| and switch contact 35. The circuit continues from contact 3| through contact 48, conductor 43 and contact 58 of switch plug 42 and through contact 34, choke coil 54 and speaker field coil IE to chassis ground. The other end of winding 28 is connected to plate 46 of rectifier tube 8.

Resistors 55 and 56 are connected across the speaker field coil I 6 to utilize part of the voltage drop across the speaker field coil as grid bias voltage, which is applied to output tube |4. Cathode 51 of rectifier tube i8 connects through radio frequency choke coil 58 and through the various coupling devices to the plates of the tubes to supply the plate voltage. Resistor 58 reduces this voltage to a suitable value to be applied to the screens of the various tubes while resistor 6| further reduces this voltage to the required value to obtain grid bias for tube 2. Variable resistor 68 is the volume control.

The rectified output of rectifier I8 is suitably filtered by condensers 62 and speaker field coil II which acts as a choke coil. The tuning of the set is accomplished by densers 88 and 88 which may be operated by a common shaft. Increased sensitivity may be obtained by introducing a small amount of regeneration in the second detector tube l3. This is accomplished by means of a small tickler coil 64 connected in the plate circuit of tube l3 and inductively coupled to the grid circuit of this tube.

In order to adapt the set for use with direct current, as for example from an automobile storage battery, the switch plug 42 is removed a switch plug 65, Fig. 3. This switch plug consists of a plurality of contacts designated 66 to 12 inclusive, and corresponding to the prongs or plug 31. Contacts 66 and 68 of switch plug 65 are connected together by conductor 13. Contacts 61 and 68 are left open. A two-conductor shielded cable 81 connects the switch plug 65 to the battery 83. Conductor 14 of the cable 81 connects at one end to contact 18 of switch plug 65 and, at the other end, to the positive pole of the battery 83. Conductor 15 of the cable 81 connects at one end to contact 1| of switch plug 65 and, at the other end, to the negative pole of battery 83. Contact 12 of switch plug connects to one end of the metallic shield 16 around the cable. The other end of this shield connects to the negative pole of the battery 83 and acts as a third conductor of the cable.

When the switch plug 65 is engaged with the contacts of group 31 and switch poles 25 and 32 are in the down position, as viewed in Fig. 1, the set is connected for direct current operation. In this case winding 22 acts as the primary of transformer l8. One end of winding 22 is connected to the negative pole of the battery 83 through contact 23 of group 31, contact 1| of switch plug 55 and conductor 15 in cable 81. The other end of winding 22, or a suitable tap thereof, as suggested at 45 in dotted lines on Fig. l, is connected to the positive pole of the battery through coil 19 and contacts 88 of interrupter 11, pole 25 and switch contact 21 of switch contact 18 01' switch cable 81.

When so connected the interrupter 11 will operate to interrupt the current through the circuit and supply a pulsating current to the winding 22 which produces an alternating current of higher voltage in windings 28 and 2| of the transformer. One end of winding 28 is connected to plate 46 of rectifier tube l8. The other end of winding 28 is connected to one end of winding 2| by means of pole 32 and switch contact 35 of switch 26. The other end of winding 2| connects to contact 24 of group 31, contact 66 and 69 of switch plug 65 by means of conductor 13 and from contact 34 of group 31 to'speaker field coil I6. In this manner windings 28 and 2| are connected in series to act as the secondary of transformer l8. The plate 48 of the rectifier tube is by-passed to contact 34 by a condenser 85. The condenser 85 being in shunt with windings 28 and 2| prevents the voltage in these windings from attaining an excessive value during that part of the cycle when no current is passing through the rectifier. This condenser should be capable of withstanding high voltages and should be of the proper capacity for efliciency and proper functioning of the interrupter contacts.

The filament current to the tubes is supplied by the battery through conductdr 14 and shield plug 65, and conductor 14 in 26, contact 28 of group 31,

16 of cable 81. The positive pole of battery 83 is 75 connected through conductor 14, contact 18 of switch plug 88, contact 28 of group 81, switch contact 21 and pole 28 of switch 28, and conductor 88 to the filaments of the tubes. The negative pole of battery 88 is connected through shield 18 of cable 81, contact 12 of switch plug 88, and contact 88 of group 81 which is connected tothe chassis.

It will be seen thatthe circuit from the positive pole of battery 88 through conductor 14, contact 18, contact 28. switch contact 21, and switch pole 28 is common to both the filament circuit and the interrupted primary circuit whereas the negative side of the filament circuit is completed to battery 83 by means of metallic shield 18 of cable 81 and the primary circuit is made through conductor 18 of cable 81. It has been found that when a common circuit is used from the battery to the set, to furnish both filament and primary current, an objectional interference is sometimes created due to the coupling of the filament circuit to the interrupter circuit through the common battery conductors. When the interference from this source is of suflicient intensity to be objectionable it may be overcome as shown in Fig. 3 by using two separate leads 18 and 18 for the negative side of the battery circuit and by making conductor 14, contact 18, contact 28, switch contact 21 and switch pole 28 of sufficiently low resistance to minimize the coupling between the two circuits. If further reduction of this coupling be required completely separate circuits may be employed.

The interrupter 11 is preferably constructed in a unit separate from the set and equipped with a plug adapted to engage in a socket on the chassis of the receiver. The shield case 18 of the vibrator is preferably lined with sound absorbing material to reduce the audible sound of the interrupter when in operation.

It will be seen that switch 28 serves as the on and off switch for the set. When the switch plug 42 is engaged with the set and the poles of switch 28 are in the up position, as viewed in Fig. 1, the set is on, and when the poles of switch 28 are in the down position the set is 011. When switch.

plug 88 is engaged with the group of contacts 31 the set is off when poles of switch 28 are in the up position, as viewed in Fig. 1, and on when the poles are in the down position. Switch 28, in conjunction with conductor 13 in switch plug 88 and conductors 48 and 44 in switch plug 42, serves to complete the circuits for operation of the set on either alternating or direct current. The circuit arrangement, Fig. 1, is such that the set may be operated on alternating current with interrupter 11 removed from the set.

It will appear that if desired this change over could be performed by plugs alone or switch alone by a suitable multiplication of contacts. It is, however, preferred to provide the contacts of group 31 in the form of prongs mounted on the edge of the base of the set, the switch plugs 42 and 88 being plugs provided with contacts in the form of sockets adapted to receive said prongs.

Fig. 4 illustrates the transformer circuit or a modified embodiment of the invention. In this modification a double pole single throw switch 88 is used and the interrupter is not incorporated in the set.

The group N2 of contacts, in the set, consists of seven contacts designated 88 to 84 inclusive. One end of winding 22 of transformer I8 is connected to contact 83. The other end of winding 22 connects to contact 82 through pole 88 and switch contact 88 of switch 88. A conductor 88 connects to switch pole 88 to furnish filament current to the tubes, the filament circuit being completed as shown in Fig. 1. One end of winding 2| connects to contact 88. The other end of winding 2| is connected to contact 88 through switch contact 88 and pole 81 of switch 88. One end of winding 28 connects to plate 48 of rectifier tube I8. The other end of winding 28 is connected to contact'88. Contact 84 is grounded to the chassis.

Cable 88. Fig. 2, is used with this embodiment of the invention for operation of the set on alterhating current. When switch plug 42 .is engaged with the contacts of group 2 and the poles of switch 88 are in the down position, as viewed in Fig. 4, the set is in operation. Winding 2| of transformer I8 acts as the primary. The connection is made by conductors 48 and 4| in cable 88, contacts 41 and 48 of switch plug 42 to contacts 88 and 88. Contact 88 connects to one end of winding 2|. The other end of winding 2| is connected to contact '88 through switch contact 88 and pole 81 of switch 88.

Winding 22 serves to furnish the filament current for the tubes. One end of winding 22 is connected to the filaments of the tubes by means of conductor 88. The other end of winding 22 connects to contact 88. The circuit is then completed through contact 82, conductor 44, and contact 88, in switch plug 42, to contact 84 which is grounded to the chassis of the set. Winding 28 acts as the secondary, one end of this winding 28 being connected to plate 48 of rectifier tube I8, and the other end connecting to contact 88. From contact 88 the circuit is completed through contact 48, conductor 48 and contact 58 of switch plug 42 to contact 8|. Contact 8| connects to radio frequency choke coil 84 and then to speaker field I8 as shown in Fig. 1.

For operation of this modified set on direct current a cable 84, Fig. 5, is provided. This cable consists of two conductors 88 and I88 and a metallic shield |8| around the two conductors. An interrupter 11, similar to that shown in Fig. 1, is connected in series with conductor I88 in cable 84. A switch plug I II is carried by one end of the cable. The other end of the cable connects to a battery 88. The positive pole of battery 83 is connected to contact I88 of switch plug III by means of conductor 88. Contact I88 is connected to the negative pole of battery 83 by means of the metallic shield I8I, around the cable. Contact I81 of switch plug III also connects to the negative pole of battery 83 through conductor I88, and coil 18 and contacts 88 of interrupter 11. Contacts I82 and I88 of switch plug I II are connected by a conductor I88 while contacts I83 and I84 are connected by a conductor I I8.

With switch plug II in engagement with contacts of group H2 and switch 83 with its poles in the lower position, as viewed in Fig. 4,. the circuit is complete for direct current operation. In this case the winding 22 serves as the primary of transformer I8. One end of winding 22 connects to contact 83 oi group 2 through contact I81 of switch plug III, conductor I88 in cable 84, coil 18 and contacts 88 of interrupter 11 to the negative pole of battery 83. The other end of winding 22 connects through pole 85 and contact 88 of switch 83, contact 82, contact I88 of switch plug III and conductor 98 of cable 84 to the positive pole of battery 83. This circuit also supplies current to the filaments of the tube in the set by means of conductor 88. The circult to the grounded ends of the filaments is made from the chassis through contact 94, contact I08 of switch plug III and through the metallic shield IOI of cable 84 to the negative pole of the battery 83. The interrupter TI is completely enclosed in a shield case 18 and a resistance BI and a condenser 82 is provided as previously described in connection with Fig. 1. Shield case 18 is connected to shield IOI of cable 84.

windings 20 and 2I are connected in series to form the secondary of transformer I8. One end of winding 20 connects to plate 46 of rectifier tube I9. The other end of winding 20 connects to one end of winding 2I through contact 90, contact I04, conductor H0 and contact I03 of switch plug III, contact 89, contact 98 and pole 91 of switch 63. The other end of winding 2I connects by means of contact 88, contact I02, conductor I09 and contact I05 of switch plug III, and contact 9I to speaker field coil I6 as in Fig. 1.

It will be seen that, in this embodiment of the invention, when poles of switch 63 are in the lower position, as viewed in Fig. 4, the set is on for either alternating current or direct current operation and with the poles of switch 63 in the upper position the set is oif in both cases. This permits the switch to be mounted on and operated by the volume control 60.

When the set is being operated on direct current, winding 22 of transformer I8 is the primary while windings 20 and 2I are connected in series to form the secondary. When the set is operated on alternating current, winding 2I acts as the primary, winding 20 as the secondary and winding 22 supplies filament current. windings 20, 2I and 22 together with other circuit values may be so proportioned that the voltages throughout the set are substantially similar whether the set is operated on direct or alternating current. In this manner all the windings of the transformer are used in either case, permitting of compact and economical design.

In Figs. 6, 7 and 8 a physical embodiment of the invention is illustrated. The set comprises a base II3 which is preferably circular and in the form of an inverted dish. The under side of this base accommodates the wiring and various small parts such as resistors and by-pass condensers. A loud speaker II4, preferably of the cone type, is mounted in the center of the base with the apex of the cone pointed towards the base. Suitable spacers may be employed between the field pot H5 and the base II3 of the set, if necessary, to bring the rim II6 of the speaker cone to a suitable height to accommodate the tubes and other apparatus mounted on the base therebeneath.

The component parts of the radio set such as the tubes II, I2, f3, I4 and I9, transformer, condensers 88 and. 89, filter condensers 62, and optionally the interrupter II are mounted on the base in the space available around the speaker field pot. The tubes and their associated coupling transformers are mounted at the periphery oi the base with their axes perpendicular to the base.

A decorative cover I I1, adapted to be supported by rim I I6 of speaker H4, is placed over the set. The cover may be fastened to rim I I6 by a number of screws II8 having decorative heads. The top surface of cover II 1 directly over the speaker cone is perforated to permit egress of sound from the speaker cone. The cover II1 extends downwardly to a point somewhat above the lower edge of base H3. The diameter of the cover II! at this point is somewhat greater than the diameter of the base II3 so as to provide an annular opening I I9 to permit egress of sound waves from the under side of speaker. In this manner the cover III forms an effective baiile for the speaker. Shaft I22 for operating condensers II and 89 and volume control shaft I2I project above the top of the cover I". Knobs I24 are carried by shafts I2I and I22 and are adapted to be easily removed. Thus it will be seen that to obtain access to the set for replacement of tubes or adjustment the screws H8 and knobs I26 are removed and cover III lifted off the set. A rotating scale I23, preferably of frusto-conical shape is carried by the shaft controlling condensers 88 and 89. The portion of cover III adjacent to scale I23 is formed as at I25 and an opening I24 provided for convenient observation of the scale by the operator.

The contacts of the group 31 are mounted on base H3 in definite order and the contacts of the switch plugs 42 and 65 are correspondingly arranged for proper engagement therewith. The contacts of the group 31 may suitably be in the form of prongs while the contacts of the switch plugs may suitably be sockets provided in said plugs.

In the modification of the invention shown in Figs. 9, 10 and 11, the tubes II, I2, I3, I4 and I9 are similar to those of the same numbers in the previously described modifications. The transformer I8 is substantially similar and comprises the windings 20, 2I and 22. The interrupter TI is substantially similar and its stationary contact is grounded. The other end of the winding I9, that is the end remote from the vibrating contact 80 is connected to one end of the winding 22. The other end oi the winding 22 is connected to a contact I27 and to a conductor I28 which serves to supply current to the filaments of all the tubes II, I2, I3, I4 and I9. The other ends of the filaments are grounded. The contact I2'I is adapted to be connected to a contact I29 by means of a switch polev I30, when in its uppermost position, as viewed in Fig. 9.

In this modification the receiver is provided with a group I3I of contacts which are analogous to group 31 and group II2 of the previously described modifications. The group I3I comprises contacts I32, I33, I34, I35, I36, I31 and I38. Contact I29 is connected to contact I32. Contact I33 is connected to a contact I 39 which is adapted to be connected to a contact I 40 by the pole I30 when in its lower position, as viewed in Fig. 9. The contact I 40 is shown connected to a suitable tap of winding 2I, although it may be connected to the upper end thereof if desired, other steps being taken to attain the necessary correlation between the windings 20, 2I and 22. Contact I34 is connected to the upper end of the winding 2I. The other end of the winding 2I is connected to contact I36. Contact I35 is connected to one end of the winding 20. The other end of the winding 20 is connected to the plate of the tube I9. Contact I 31 is connected to the field coil I6 of the speaker I 5 in substantially the same manner as described heretofore. Contact I38 is grounded.

In order to adapt the set for use with direct current supplied by a battery I4I, a switch plug I42 is employed having contacts I43, I44, I45, I46, I47, I48 and I49 corresponding to contacts I32, I33, I34, I35, I36, I31 and I38 respectively,

and winding 22 serves as a secondary.

tacts I32, I33, I34, I35, I38,

these contacts being engaged in the order stated. Contact I41 is connected to contact I48. Contact I45 is connected to contact I48. Contact I43 is connected by a conductor I50 to the positive plate of the battery I4I. Contact I49 is connected to the negative plate of the battery MI by means of a shielding coating I5I provided around the conductor I50- When the switch plug I42 is connected to the group I3I of contacts, the negative plate of the battery MI is grounded through the shield I5I and contacts I49 and I38.- Contact I44 being left open, contacts I33 and I39 are disconnected and the off position of switch I30 is its lower position, as viewed in Fig. 9. The positive plate of-the battery I is connected through contacts I43, I32 and I28, the switch pole I30 (in its upper position), and cgntact I21 to the winding 22 and the conductor The current passing through the winding 18 actuates the interrupter 11 as described before, and winding 22 serves as the primary for the transformer I8. Windings 20 and 2| are connected in series through contact I35, contact I46, contact I45 and contact I34. When employed with alternating current. switch plug I52, shown in Fig. 11, is employed. This plug oomprises a series of contacts I53, I54, I55, I58, I51, I58 and I59, corresponding respectively to con- I31 and I38 of the group I3I. Of these contacts I53, I55 and I59 are left open corresponding to the isolation of contactsl32, I34 and I38. Contacts I54 and I51 are connected to the prongs of the plug I which may be inserted in any suitable power outlet supplying alternating current. Contacts I56 and I58 are connected. When the switch plug I52 is applied to the group I3I, contacts I54 and I51 communicate to contacts l33and I38 so that the winding 2 I, or the lower portion thereof, is energized when the switch pole I30 is moved to its lower position as viewed in Fig. 9. this being the on position for the alternating current hook-up. When the switch pole I30 is moved to its upper position, the set is off. Contact I53 is isolated supplying filament current to the conductor I28. This current passes through the filaments to ground and also passes through winding 18 and contact 80 to ground. This current is, however, relatively slight and does not affect the vibrator 11. Winding 20 is connected through contacts I35, I58, I58, I31, and thus to the field coil in the manner previously referred to.

An important result obtained by this modification is that the production of radio frequency disturbances by the vibrator 11 is reduced to a minimum, particularly owing to the manner in which the interrupter is directly grounded. In order further to reduce interferences it is preferred to provide choke coils I8I and I82 in the line I28. It will be noted that coil I82 is provided between tubes I2 and I3 and that coil I6I islocated on the'output side of tube I4. The inductances of the choke coils I8I, I82 are correlated to the resistances of the filaments to prevent voltage disturbances from passing along the conductor I28 in the output-to-input direction. The choke coils I8I, I82 combine with the filaments to provide a filter circuit containing inductances and resistances. Filtering action is greatest at thefilaments of the tubes II and I2, which is important since disturbances in these tubes are capable of greater amplification in the final output.

Other important effects obtained by this modification are its great simplicity, considering the results attained, and the fact that the switch employed may be of simple and heavy construction while taking up a very small amount of space.

Although the invention has been disclosed in connection with the specific details of preferred embodiments thereof, it must be understood that such details are not intended to be limitative of the'invention except in so far as set forth in the accompanying claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. In a radio receiver adapted for operation by alternating current and relatively low voltage direct current, in combination, thermionic tubes having filaments and plate circuits, a filament and plate supply transformer having a winding adapted to supply filament current when operating on alternating current, another winding adapted to supply high voltage plate current during both alternating current operation and direct current operation, and a winding which is adapted to serve as a primary during alternatingcurrent operation and another winding which is adapted to serve as primary and receive pulsating direct current during direct current operation, means for supplying filament current direct from the source of current supply during direct current operation, a loud speaker having a field adapted to be energized by the plate current during alternating current operation, circuits connecting the thermionic tubes, transformer windings and current supply, and switching means for breaking certain circuits and completing other circuits to adapt the receiver for operation with either alternating or direct current supply.

2. Ina radio receiver adapted to be operated from an alternating current and. a direct current supply, in combination, thermionic tubes having filament and plate circuits, a transformer adapted to supply filament and plate current, said transformer having at least three windings, switching means on said receiver adapted to connect one transformer winding to said filament circuit, another winding to said plate circuit, and still another winding to alternating current supply, and alternately to connect one of said windings and said filament circuit to a source of direct current and two of said windings in series with the plate circuit, and means adapted to produce pulsations in the direct current supply.

3. In a combinedhigh' voltage alternating current andlow voltage direct current operated receiverincluding a dynamic loud speaker having a field coil, a transformer, and thermionic tubes requiring filamentcurrent and high voltage plate current, means for supplying high voltage alterhating current to the transformer, means for supplying low voltage direct current alternatively to the transformer, means for producing pulsations in the low voltage current to render same transformable, rectifying devices receiving high voltage alternating current from said transformer and supplying pulsating high voltage energy, and

a common filtering system for reducing the pulsations tlrprovide said plate current, which system includes a. reactance the field coil of said loud speaker. a.

4. In a combined alternating current and low voltage direct current operated receiver having thermionic tubes requiring filament current and plate current of higher voltage, means for sup- 75 plying alternating current to the receiver, separate means for supplying low voltage direct current alternatively to the receiver, means for producing pulsations in the low voltage direct current to render same transformable, transforming and rectifying means to supply said plate current of higher voltage during both alternating current and low voltage direct current operation, means for supplying the low voltage direct current directly as filament current to the thermionic tubes during low voltage direct current operation, and means for deriving filament current from said transforming means during alternating current operation.

5. In a combined alternating current and direct current radio receiver, means for supplying alternating current to the receiver, separate means for supplying alternatively direct current to the receiver, separate circuits for said supplies, and a single switch for both supplies for turning on and of! the supply of current to the receiver, and means selecting the separate supply circuits to said receiver through said switch such that the "on and off" positions of the switch when connected to one supply circuit are the ofi" and "on" positions, respectively, when connected to the other supply circuit.

6. In a combined alternating current and low voltage direct current radio receiver, in combination, an amplifier, a loud speaker, separate means for supplying alternating current and low voltage direct current, a transformer having a plurality of windings adapted to be connected to give plate and filament voltages for the amplifier, and a switch for turning on and off the supply of current to the receiver adapted in one position to connect the transformer for direct current operation and in another position to connect the transformer for alternating current operation, the switch in the "on position for direct current interrupting the alternating current supply and in the on" position for alternating current operation interrupting the direct current supply.

7. In a combined alternating current and low voltage direct current radio receiver, in combination, an amplifier, a loud speaker, means for supplying high voltage alternating current, means for supplying low voltage direct current, means for deriving plate and filament current from said supplying means for the receiver and loud speaker, a single switch for connecting both supplying means to said last mentioned means, and means, selectively connecting the separate supply circuits to said switch such that the "on" position for the direct current supply is the "off position for the alternating current supply and the "off position for the direct current supply is the on" position for the alternating current supply.

8. In a radio receiving system, the combination with a signal receiving and reproducing means comprising a plurality of amplifying stages connected in cascade which include electron discharge tubes having heating elements, of A and B-power supplies having a common multi-winding transformer, one winding of which serves as a primary for energizing the same from a relatively high voltage source of alternating current, and a second winding connected to supply heating current for said tubes, and switch means associated therewith for connecting said second winding to serve as a primary for said transformer when energized from a relatively low voltage source of intermittent current, said switch means including relatively movable contact members for disconnecting the first-named winding from the high voltage source of alternating current when said second winding is a primary and for supplying the heating current in parallel with that energizing said second winding.

9. In a combined alternating current and low voltage direct current operated receiver having thermionic tubes requiring filament current and plate current of higher voltage, means for supplying alternating current to the receiver, separate means for supplying low voltage direct current alternatively to the receiver, means for producing pulsations in the low voltage direct current to render same transformable, transforming and rectifying means to supply said plate current of higher voltage, a single filtering system for filtering the higher voltage current during alternating current and low voltage direct current operation, means for supplying the low voltage direct current directly as filament current to the thermionic tubes during low voltage direct current operation, and means for deriving filament current from said transforming means during alternating current operation.

10. A radio receiver adapted for operation with relatively high voltage alternating current supply or with relatively low voltage direct current supply, comprising thermionic tubes having plates and filaments, a transformer having a winding, switching means adapted to connect said filaments and said winding to a source of low voltage direct current during direct current operation and to connect the filaments to said winding during alternating current operation, and vibrating means for producing pulsations in the direct current'supply to said winding of the transformer during direct current operation.

11. In a combined alternating current and battery operated receiver having thermionic tubes requiring filament current and plate current of higher voltage, a single transformer for supplying said plate current, means for supplying alternating current to said transformer, separate means for supplying battery current alternatively to said transformer, means for producing pulsations in the battery current to render same transformable, rectifying means connected to said transformer to rectify said plate current of higher voltage, a single filtering system for filtering the rectified higher voltage current during alternating current and battery operation, and a secondary winding on said transformer for supplying filament current during alternating current operation.

12. In a radio receiver, in combination, thermionic tubes having plates and filaments, a single transformer having two windings adapted to serve as primaries and two windings adapted to serve as secondaries, last said two windings being capable of supplying two secondary currents, one of low voltage directly connected to said filaments and one of high voltage connected to said plates, selective connecting means for connecting said transformer to a source of alternating current or a source of direct current, manual switching means between said connecting means and said transformer for turning the receiver on and off, said connecting means and switching means cooperating to supply alternating current to one primary winding and direct current to the other primary winding, and means in the direct current supply circuit for producing pulsations in said direct current.

13. In a radio receiver, in combination, thermionic tubes having plates and filaments, a transformer having two windings adapted to serve as primaries and two windings adapted to serve as secondaries, last said two windings supplying two secondary currents, one of low voltage directly connected to said filaments and one of high voltage connected to said plates, selective connecting means for connecting said transformer to a source of alternating current or a source of direct current, manual switching means between said connecting means and said transformer for turning the receiver on and off, said switching means connecting the alternating current to one primary and the direct current to the other primary winding, and means in the direct current supply circuit for producing pulsations in said direct current.

14. In a radio receiver adapted for alternating current and battery operation, in combination, thermionic tubes having plates and filaments, a transformer having two windings adapted to serve as primaries and two windings adapted to serve as secondaries, one of said secondaries being connected to said plates, the other secondary being adapted to supply filament current during alternating current operation, means for connecting said primaries to alternating current and the battery alternatively, a manual switch for turning the receiver off and on and for connecting the filaments to the battery during battery operation and for connecting last said secondary to the filaments during alternating current operation, and means for creating pulsations in the battery current supplied to the primary during battery operations.

15. A radio receiver adapted for operation by alternating or direct current, comprising a transformer having a filament supply winding and a plate supply winding, the first said winding being adapted to serve as a primary during direct current operation and as a secondary for the supply of filament current during alternating current operation, vibrating means for rendering direct current pulsating, a filament circuit including said winding, said vibrating means and a filament in series, and switching means adapted to connect a supply of direct current across said filament and across said winding and vibrating means in series, and to connect a supply of alternating current to the first said winding during alternating current operation, said vibrating means being actuated by said direct current and non-responsive to the secondary filament current.

16. In a combined alternating current and low voltage direct current operated receiver having thermionic tubes requiring filament current and plate current of higher voltage, means for supplying alternating current to the receiver, separate means for supplying low voltage direct current alternatively to the receiver, means for producing pulsations in the low voltage direct current to render same transformable, a single transformer and rectifying means to supply said plate current of higher voltage during both alternating current and low voltage direct current operation, means for supplying the low voltage direct current directly as filament current to the thermionic tubes during low voltage direct current operation, and means for deriving filament current from said single transformer during alternating current operation.

1'7. In a combined alternating current and low voltage direct current operated receiver having thermionic tubes requiring filament current and plate current of higher voltage, means for supplying alternating current to the receiver, separate means for supplying low voltage direct current alternatively to the receiver, means for producing pulsations in the low voltage direct current to render same transformable, a single transformer and rectifying means to supply said plate current of higher voltage, a single filtering system for filtering the higher voltage current during alternating current and low voltage direct current operation, means for supplying the low voltage direct current directly as filament current to the thermionic tubes during low voltage direct current operation, and means for deriving filament current from said single transformer during alternating current operation.

18. In a combined high voltage alternating current and low voltage direct current operated receiver having thermionic tubes requiring filament current and plate current of higher voltage, a single transformer for supplying said plate current, means for supplying high voltage alternating current to said transformer, separate means for supplying low voltage direct current alternatively to said transformer, means for producing pulsations in the low voltage direct current to render same transformable, rectifying means connected to said transformer to rectify said plate current of higher voltage, a single filtering system for filtering the rectified higher voltage current during alternating current and direct current operation, a secondary winding on said transformer for supplying filament current during alternating current operation, and means for supplying low voltage direct current directly to the filaments of said thermionic tubes during direct current operation.

19. In a radio receiver, in combination, thermionic tubes having plates and filaments, a single transformer having two windings adapted to serve as primaries and two windings adapted to serve as secondaries, last said two windings being capable of supplying two secondary currents, one of low. voltage connected to said filaments and one of high voltage connected to said plates, selective connecting means for alternatively connecting a high voltage alternating current to one primary winding and a low voltage direct current to the other primary winding, and means in the direct current circuit for producing pulsations in said direct current.

0. In a radio receiver, in combination, thermionic tubes having plates and filaments, a transformer having two windings adapted to serve as primaries and two windings adapted to serve as secondaries, la'st said two windings supplying two secondary currents, one of low voltage connected to said filaments and one of high voltage connected to said plates, a source of alternating current, a,source of direct current, selective connecting means for alternatively connecting said source of alternating current to one primary winding and said source of direct current to the other primary winding, and vibrating means in the direct current supply circuit for producing pulsations in the direct current.

21. In an electrical power supply system for supplying alternatively high voltage direct current from a source of high voltage alternating current and from a source of low voltage direct current, in combination, a transformer having a primary adapted to be energized from said source of high voltage alternating current, a primary adapted to be energized from said source of low voltage direct current, a continuously operating current interrupting means in series with last said primary, and a high voltage secondary wind- 16 ing, rectifying and filtering means connected to last said winding.

22. In a power system for the operation 01' thermionic tubes having plates and filaments, alternatively from a source of high voltage alternating current and a source of low voltage direct current, in combination, a transformer having a primary winding adapted to be energized from -a source of high voltage alternating current, a

primary winding adapted to be energized from a source of low voltage direct current, a continuously operating current interrupting means in series with last said winding, a high voltage secondary winding, rectifying and filtering means connecting last said winding to said plates, and means for supplying filament current to said thermionic tubes from said transformer.

EDWARD F. ANDREWS. 

